mmc/dwmmc: use bounce buffer for data exchange between CPU and MMC
controller

Bounce buffer implementation takes care of proper data buffer alignemt
and correct flush/invalidation of data cache at once so we no longer
depend on input data variety and make sure CPU and MMC controller deal
with expected data in case of enabled data cache.

Bounce buffer requires to add its definition (CONFIG_BOUNCE_BUFFER) in
board configuration, otherwise corresponding library won't be compiled
and linker will fail to build resulting executable.

Difference since v1 - fixed compile-time warning with type casting to
"void *":
====
passing argument 2 of ‘bounce_buffer_start’ discards ‘const’ qualifier
from pointer target type
====

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Mischa Jonker <mjonker@synopsys.com>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Amar <amarendra.xt@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
Cc: Andy Fleming <afleming@gmail.com>